Spencer, Emily, Hanna and Aria investigated Mona’s murder, hoping to prove Ali was responsible in the hopes of saving Spencer from prison on Pretty Little Liars’ winter premiere, “Through a Glass, Darkly.”

PLL “Through A Glass Darkly” Recap

It has been three months since Mona’s murder on Thanksgiving, and everyone has gathered for Mona’s funeral. It’s an empty casket, full of trinkets and other things Mona’s mother placed in it instead of a body. As the group exits the church, Ali (Sasha Pieterse) shows up, wearing a bright pink dress, to talk to Mona’s mother. She wants to tell Mrs. Vanderwaal (Sydney Penny) that she had nothing to do with Mona’s murder, but Mrs. Vanderwaal doesn’t believe her and slaps her instead. “Where is my daughter?” she asks, crying.

While Ali is still walking around town a free girl, Spencer’s legal troubles are flaring up again. Bethany Young’s family wants to have her bail revoked in light of new evidence. It turns out that Detective Wilden suppressed a witness statement given to him by Mrs. DiLaurentis, placing Spencer (Troian Bellisario) in the backyard with a girl wearing Ali’s clothes (supposedly Bethany Young). Both Spencer and Toby (Keegan Allen) – who is now officially a cop and friends with Detective Tanner (Roma Maffia) – are unusually accepting of the theory that Detective Wilden suppressed evidence, but, at the same time, both are terrified that this could land Spencer behind bars. They gave the cops the letter they discovered in Ali’s room at Christmas, the one that proved Ali knew Bethany and had invited her over on Memorial Day Weekend, but the cops still think Spencer is guilty of Bethany’s murder. The only way to convince the cops of Spencer’s innocence and get them to suspect Ali of killing Bethany is to try to prove that Ali killed Mona. Then the cops might look at the murders as linked and back off Spencer.

Aria The Hacker

While Hanna (Ashley Benson), Emily (Shay Mitchell) and Spencer focus on solving Mona’s murder, Aria (Lucy Hale) has more personal matters to attend to. Firstly, her brother, Mike (Cody Christian), isn’t speaking to her, at least not about Mona’s death, and she’s worried about him. Luckily, Ezra (Ian Harding) needs some help building shelves for the new Brew, which he bought, and volunteers to ask Mike to help him and maybe get Mike to open up. But, Aria has another problem: she hasn’t gotten into college, and she’s lying to Ezra about it. She thought she was a shoe-in for Oberlin, and, after receiving a rejection letter, she goes straight to Caleb (Tyler Blackburn). She wants him to hack into the Oberlin database to find out why she didn’t get in. She needs to know if she really just didn’t get in or if A had something to do with it.

Caleb agrees to help, but only on the condition that she try to learn a few things too. For example, he shows her the laptop they recovered from Mona. He’s still trying to decrypt the data – Mona made up her own code to lock her files, so it’s taking him longer than usual. For some reason, Aria ends up with Mona’s laptop (or Caleb’s fancy decryption laptop, it was unclear which one she had) when she’s attacked in the empty Brew – she’s there to pick up her brother. A hooded figure attacks Aria, incapacitating her long enough to steal the laptop and run. When Aria tells Emily about the attack, she says she’s sure it was Ali under that hood.

Did Ali Kill Mona?

To investigate Mona’s murder, Hanna, Emily and Spencer split up. Hanna decides to try to find Mona’s body while Emily and Spencer pay Jason (Drew Van Acker) a visit in an effort for him to retract his statement to the police, which gave Ali an alibi. Desperate, and without any leads, Hanna contacts Ms. Grunwald (Meg Foster), the Ravenswood psychic who saved Ali on the night she disappeared, in the hopes that she might be able to use her gifts to locate Mona’s body. Unfortunately, she can’t, but she is able to tell Hanna that Mona is cold, alone, and covered in dirt and bugs. She doesn’t contradict Hanna when Hanna tells her she thinks Ali killed Mona.

Emily and Spencer have better luck with Jason. Spencer pleads with him to tell the truth. He and his father told the cops that Ali was with them all night when Mona was killed, but he knows that’s not true. He says he’s stuck – Ali is his sister after all. But, Spencer reminds him that she, too, is his flesh and blood and right now, Ali is the bad guy, not her. Jason doesn’t leave Spencer with much hope, but her talk stays with him, and he later confronts Ali, who insists that Spencer, Emily, Aria and Hanna were all just trying desperately to frame her for murder because they want her gone.

If Jason fails to tell the cops the truth, Emily’s got a backup plan. While they were at the DiLaurentis house, she snuck into Ali’s room and stole her hairbrush. All they have to do, she says, is plant some hairs at Mona’s house and convince the police to go over the crime scene again. If Ali’s DNA is found at the scene, they’ll have to look at her as a suspect. Spencer isn’t convinced. Not only is it against the law, but the cops already found Mona’s DNA in Ali’s car and they remain convinced of her innocence. Still, faced with the harsh reality of a life in prison, Spencer agrees to go through with the plan. While looking for somewhere to plant the hairs, Spencer discovers a surveillance camera hidden behind a vent across the front door. They don’t need to plant evidence. Mona caught the entire murder on tape.

Hanna suggests to Mrs. Vanderwaal that Mona was so afraid of Ali, she once told Hanna she was going to set up some cameras in her house, and the police find a tape of the murder. (Luckily, the cameras ran out of power weeks ago, so Spencer and Emily weren’t caught on tape trying to plant evidence.) Mona’s murderer isn’t clearly seen in the videos, but Mona is seen being stabbed by a hooded figure with blonde hair. The cops bring Jason in to view the video, and he confirms that it could be his sister. She wasn’t with him on the night Mona was murdered, he says, and he believes she could have killed Mona.

Ali Is Arrested

Hanna, Emily, Spencer and Aria all gather to watch Ali get arrested for Mona’s murder. They stand united, even as Ali warns them that she isn’t A, and, once she’s gone, they’ll be next. Later, the police tell Spencer that, in light of Ali’s arrest, the DA is dropping all charges against her.

After Ali’s arrest, Emily rushes to the airport to say goodbye to Paige (Lindsey Shaw). She’s hoping that with Ali behind bars, Paige’s parents can be convinced that Rosewood is safe again and will let Paige stay until graduation. Paige isn’t convinced, and she leaves for California.

Finally, the girls gather together on Spencer’s porch and talk about one day leaving Rosewood, and hopefully ending their senior year safely and A-free. A fireworks show from a local carnival starts, and, while at first the girls are enchanted, they become terrified when the fireworks make an ‘A’ in the sky and sparks rain down on them. It could have been set up by Ali before she was arrested, but who knows…

Pretty Little Liars airs Tuesdays at 8 p.m. on ABC Family.